The Earliest Known Metazoans

In 1964 S.B. Mirsa, a graduate student at Memorial University in Newfoundland, discovered a group of well-preserved fossilized soft-body animals. Subsequent research revealed the fauna were from the Ediacaran Period 635-542 million years ago.

Ediacaran was not officially recognized as a geological period until 2004, the first new period in over 120 years. The period is named after the Ediacaran Hills in Southern Australia, which take their name from aborigine Idiyakra, “water is present”, the type locality for the fauna. Over the globe 25 localities have been discovered that possess fossils from this period. The localities are typically grouped into three types based assemblage of organisms they possess. These organisms represent the oldest known complex multicellular organisms predating the Cambrian Explosion by several million years.

The site that Mirsa discovered and described is Mistaken Point on the southern tip of Avalon Peninsula in Newfoundland. The deposit dates to 550-560 mya and of all the localities has the largest quantity of fossils. Organisms preserved here inhabited a muddy seafloor and were covered by a fine-grain volcanic ash that preserved the fossils in exquisite detail.

I mention Mistaken Point for two reasons. First the biota were deep-dwelling and well below the photosynthetic zone. Perhaps not as deep as the typical organisms we discuss here, they likely represented organisms on a continental shelf fauna. The second reason I mention this is that the recent American Society for Limnology and Oceanography meeting in St. Johns Newfoundland allowed me the oppurtunity to visit this Mecca of Science and see the fossils first hand.

River be damned! The Ediacaran awaits!

The trip require a a quarter day drive down the Newfoundland coast on the Irish Loop. A turn off the highway had colleagues and I driving down a 9 mile unpaved road in a rental hybrid poorly equipped for such an adventure. At the parking lot a 4-6 mile round trip hike is awaited us. The hike over rolling hills right on the beautiful Avalon coast while not strenuous did require wading across a sizable stream (small river?) with Newfoundland’s finest and potentially coldest waters. A hiker and son returning the opposite direction did much to curtail our enthusiasm for the site. Both expressed disappointment, claiming to see only a few small and poorly preserved things.

Thankfully the hiker and son were wrong. The Mistaken point fauna is nothing short of spectacular! The fossils are large, dense, interesting, and well-preserved. I stood in total awe realizing I was viewing a organisms that inhabited the deep 560 million years ago. These animals were the among the first complex organisms and standing there I was viewing a pivotal moment in the history of life.

Now for the best part! Below the fold are pictures of these organisms.

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, created to facilitate research to address fundamental questions in evolutionary science. He has conducted deep-sea research for 11 years and published over 40 papers in the area. He has participated in dozens of expeditions taking him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses mainly on marine systems and particularly the biology of body size, biodiversity, and energy flow. He focuses often on deep-sea systems as a natural test of the consequences of energy limitation on biological systems. He is the author and chief editor of Deep-Sea News, a popular deep-sea themed blog, rated the number one ocean blog on the web and winner of numerous awards. Craig’s popular writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

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Way cool! I agree, they look a little like sea pens or some relative of a cnidarian.

I can’t wait to go into the field with my kid and show him fossils. I did it all the time growing up in Iowa. Found fossil shark teeth and shells all over the place at Wildcat Dens at Maquokata Caves. Probably the best hidden wonder in the state!

I couldn’t expect any lineages from 590 mya to look even remotely the same today. But ever since the April publication of a paper in Nature that identified ctenophores as the oldest multicellular lineage that we have identified, I wonder if they were around in the Ediacaran too.

The discovery was made in the month of June, 1967 on one afternoon when I was hungry,tired and feeling lonely after a day’s field work and was having snacks sitting on the slab containing the imprints. More in my upcoming book “The Story of an Ordinary Indian”

Yes, St. John’s was very kind to me. I had stayed in Portugal Cove South for my field work in 1967. wonderful people. I cherish my memories of those days.I am happy that you are pursuing research on the fauna so vigorously. Please change the year of discovery if possible. Best Wishes.